Alternating-current electric meter.



Patented D'ec. l6, I9C2. C. P. STEINMETZ.

ALTERNATING CURRENT ELECTRIC METER.

(Application filed Apr. 28, 1902.)

"1 WW I Q C TNVENTU ghar'lesl 'is@inmej? T Li UNITED STATES ATENT 0FFICE.

CHARLES P. STEINMETZ, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ALTERNATlNG-CURRENT ELECTRIC METER.

SPECIFICATION forming part of Letters Patent No. 716,351, dated December16, 9

' Original application filed February 11, 1898, Serial No. 669,901.Divided and this application filed April 28, 1902. $erial No. 104,970.(No model-l To all whom it may concern:

Be it known that I, CHARLES P. STEINMETZ, a citizen of theUnited States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new i and useful Improvements in Alternating-Current Electric Meters, (division of my prior application, SerialNo.'669,901, filed February 11, 1898,) of which the following is aspecifi cation.

In alternating-current systems in which power is sup plied to inductivetranslating devices--for example, such as induction-motors-apart of thecurrent is almost invariably wattlessthat is, it does not representpower delivered. Nevertheless, since wattless currents represent powerconsumed on the lines and in transformers, because of the 0 R loss, andsince such currents consume generator capacity it is fair that a chargeshould be made, though perhaps at a smaller rate than the rate chargedfor actual power delivered for this loss in the system, since such acharge would form a check on customers using motors too large for thework demand upon them and running therefore at light loads withconsequent excessive lagging current. Moreover, the fact that somecharge is made for wattless current constitutes an inducement forcustomers to cut out of circuit entirely except when in actual use allinductive apparatus, such as transformers or motors, which take at noload an excessive lagging current.

It is the object of my invention to provide a meter recording not onlythe power delivered, but also a part at least of the power lost on theline due to the lagging or wattless currents. I accomplish this objectby prodncing in some of the actuating-coils of a meter, such as theThomson recording-wattmeter or an induction wattmeter or whatevertypemay be preferred, a relative inductive reactive effect and aresultant relative shifting of the magnetomotive forces, which act onthe armature to cause it to actuate the registering or indicatingmechanism. In a Thomson recording-wattmeter, for instance, by properlyadjusting the relative amount of reactance and non-inductive resistancein the potential circuit of the instrument the amount of laggingcurrents recorded can be adjusted as desired, and consequently acorresponding rate of charge can be established.

The power in an alternating-current circuit is equal to volts intoamperes multiplied by the cosine of the phase angle between the voltsimpressed on the circuit and the current flowing. The readings in arecording-watt meter are proportional to the current in the potentialcircuit-that is, the current due to the difference of potential acrossthe mains into the main current multiplied by the cosine of the angle ofphase difference between these two currents. Moreover, if the potentialcircuit is in phase with the impressed volts the reading of thewattmeter will be proportional to the power.

I have found that if we insert in the potential circuit of the wattmetera suitable inductive reactance and adjust it so as to cause themagnetism due to the current in the potential circuit to lag, say,twenty degrees behind the phase which it would have were the instrumentto register the actual energy consumed, and then so adjust the wattmeteras to read correctly at non-inductive load by properly proportioning thewindings or adjusting the recording or registering mechanism, thereading of the instrument will not be volts by amperes by cosine of thephaseangle between the impressed volts and the resultant amperes, butwill be volts by amperes by cosine of an angle twenty degrees less thanthe angle of lag in the circuit. The cosine of this angle is obviouslygreater than the cosine of the phase-angle itself.

For example, suppose the lag of the current due to the inductive load istwenty degrees. Then the power delivered is volts by amperes by cosineof the angle of twenty degrees, the cosine of twenty degrees being 94-,that is, in this instance, the actual power delivered is slightly lessthan the apparent power.

Let us consider what would be the readings of the instrument when adevice having inductance or an inductive resistance is included in thepotential circuit of the wattme- IOQ ergy consumed in the circuit, sincethe energy consumed with a non-inductive load on the circuit is volts byamperes,while the readings of the instrument would be volts byamperesby.94. Therefore theinstrumentshould be readjusted to give atnon-inductive load the same readingthat is,volts by amperesas if theinductive resistance was omitted from the potential-current circuit. Thein strument is therefore made to read higher than the equation wouldmake it read in the ratio which unity bears to the cosine of twentydegrees. Suppose the main-line current lags by 00. Then the differenceof phase between the current in the mainline and that in the potentialcircuit is (cf-20) and the equation would give, for themeter-registration, volts by amperes by cos. (of-40); but as the meterhas been readjusted, as above described, it results that it(s geadingwould 7 Cos. 5c 20) be volts b amperes by m With the reactance causing alag of twenty degrees in the potential circuit, the instrument beingadjusted to read correctly at noninductive loads, the reading of theinstrument will be at twenty degrees load lag, volts Cos. (20 20) 1 Cos.0 or Cos. 20 Cos. 20

1.06+, so that the instrument will register a small percentage over whatit would register with the inductance eliminated from the potentialcircuit, and therefore there would be a small charge for wattlesscurrent at a time when the lag caused by load is relatively small. Ifthe lag of the current is comparatively great-for example, say, sixtydegreesthe power of the circuit is one-half the volts by amperes, sincethe cosine of sixty degrees is one-half. The reading of the instrumentwould be in this case volts by amperes by Cos. 20 5%, or volts byamperes by am peres by or volts by amperes by by .83. In this case itwill be apparent that the instrument registers about 1.66 times theactual power delivered. In this case the charge for wattless currents isevidently almost two-thirds of the charge for energy-current. If the lagof the circuit is eighty degrees, then the instrument will indicatevolts 3%, which is volts by amperes by Z-Z-that is, the instrument inbyamperes by stead of charging .17+ times the volt amperes charges .54times the volt amperes. In this case the charge is for the actual powerand forsomething over one-third of the wattless currents.

By adjusting the relative amount of inductance in the potential-currentcoils of the wattmeter we can vary the readings of the instrument so asto charge at difierent rates of increase according to differentadjustments made. By cutting out entirely the inductive resistance orreactance we can change the instrument back into a wattmeter of theordinary type, which registers simply the actual power supplied, inwhich case the reading of the recording-wattmeter becomes againpotential current by main current by cosine of the angle between thetwo. By properly adjusting the non-inductive and inductive resistance ofthe potential circuit of the wattmeter in different proportions we getdifferent readings, so that the instrument when combined with aregulable inductive and a regulable non-inductive resistance in itspotential-current circuit becomes a multiplerate meter-that is, a metercapable of giving difierent readings in accordance with the relativeamount of reactance in its potentialcurrent circuit. The same principlecan be applied to any recording-wattmeter based on the mutual action ofpotential-current coils and the main current-coils. Forinstance, in theinduction wattmeter where the currents in the two coils areapproximately ninety degrees separated from each other and act on anarmature wound with closed coils or on simplya disk of conductingmaterial in which eddy-currents are generated the same effect may besecured by making the potential current lag more than ninety degreesbehind the impressed electromotive force, as by producing an inductivereactive effect in certain of the coils of the instrument, and byadjusting this inductive effect be obtained.

It results from a motor constructed as described that a customer maybe'given a certain discount for taking leading currents; but this is notobjectionable, since such currents tend to raise the power factor of thesystem.

Referring to the drawings, Figure l illustrates my invention inconnection with a Thomson recording-wattmeter, in Which A B representconstant-potential mains supplied with energy or through intermediationof transforming apparatus; and Fig. 2 represents diagrammaticallytheapplication of my invention to an induction-wattmeter.

In Fig. 1, A indicates the armature-coils of the wattmeter, and K Kindicate the fieldmagnet coil of the wattmeter, here shown as of a usualand well-known construction. X is the shaft which carries thearmature-coils, supported in the usual manner in adjustable jewel-bearin gs. M is the da m ping-disk acted upon by the permanentmagnets M M. LL are incandescent lamps or other similar devices arrangedin multiple on the constantpotential circuit A B. C is the commutator ofthe armature, upon which rest brushes C, by which commutator and brushes2. current in multiple with the mains A B and corresponding in magnitudeand phase to the electromotive force impressed on the translatingdevices may be supplied to the coils A. D

represents any of the well-known forms of reglstering mechanism, such asa train of gearratus a meter of the multiple-rate type.

ing with indicating-dials. R is an adjustable non-inductive resistanceof any well-known type, and R is an inductive resistance or reactancedevice, such as is involved in my invention. It will be noticed thatthis reactance deviceis adjust-able. The points of contact of the coilsover which the switches pass are connected at such points of the windingof the inductive resistance with relation to the non-inductiveresistance, the instrument, and the circuit in which it is connectedasto permit the adjustment which renders my appay placing the switch-armS on the second contact, as shown, enough of the coils of the inductiveresistance will be in circuit with the armature A and potential circuitI to cause a lag of the current in the armature of, say, twenty degrees.When placed on the next contact to the right, a lag of thirty degreeswould be produced in the armature-circuit, and so on.

Turning to Fig. 2, which illustrates, as I have stated, my invention inconnection with an induction-Wattmeter in outline, T represents atransformer through which energy is supplied at constant potential andlowered pressure to the circuit A B in which are arranged incandescentlamps or other translatingdevices l H. Of course the energy may besupplied to the lamps directly without the use of a transformer;

i main-current coils of the wattmeter, and S S represent the potentialcoils of the wattmeter, connected across the mains A B These coilsconjointly act upon an armature A here shown as a cylinder of conductingmetal. R is an inductive resistance connected, as usual, in the circuitwith the potential coils to produce a lag of current in i the potentialcoils as near ninety degrees as gle of lag.

that the reading should correspond toE 0 cos.

possible; but the current in the potential coils with the arrangementthus far described can never lag quite enough behind the impressedelectromotive force to cause the meter-reading at all loads to be E 0cos. m when E is the electromotive force, 0 the current, and (p the an-My invention requires, however,

(go-H9) or, say, E C cos. p+20.) It therefore becomes necessary toartificially retard the phase of the current flowing in the coils S S Iprefer to produce this result by shunting them with a device which actsto retard the phase of the current therein-such, for example, as anon-inductive resistance, (shown at R This device will divide thecurrent in the branch circuit already lagging by, say, eightyfivedegrees into a leading component and a lagging component. The laggingcomponent, which will obviously be behind the current in the coil R inphase, will pass through the coils S S By properly adjusting the effectof this phase-retarding device, which is here shown as an adjustableresistance, the lag of the current in the potential coils maybe- (3 Crepresent the made, for example, one hundred and ten degrees. i i

In addition to the resistance R I may wind a coil or set of coils S? Son the magnetic circuit of the coils S S themselves with or without anadjustable resistance R, will tend to heat back the flux due to thecoils S S and to retard it in phase, as is well understood in the art,and produce an additional lag in the magnetism due to the potentialcoils.

Though I have shown two separate devices acting to retard this fluxworking conjointly, it is obvious that either one alone may be used.

By varying the amount of resistance in these respective sets of coils,since the amount of current flowing through them is thus varied, we canvary their relative magnetizing effect, and thus in turn effect thedisplacement in phase of their resultant magnetic flux.

Of course any well-known arrangement of varying the number of turns ineither or both of these sets of coils may be used with the same effectin substance as the variable noninductive resistances produce in eitheror both.

I do not limit myself to any particular form of alternating-currentelectrical measuring instrument, since I consider that I am the inventorof the broad apparatus for so shifting the relationship of the actuatingmagnetomotive forces which set in motion the armature of analternating-current indicating or registering instrument, such as ameter or galvanometer, as to establish such lag, either in current ormagnetomotive forces, as will when the registering mechanism is properlyadjusted record a predetermined amount of wattless current in analternating-current circuit.

What I claim as new, and desire to secureby Letters Patent of the UnitedStates, is-

1. In an alternating-current wattmeter, or indicator, the combination ofthe actuatingcoils, a reactance device included in one of said coils andregistering or indicating mechanism actuated by the currents in saidcoils and so adjusted as to register or indicate a proportionate amountof wattless current.

2. In an alternating-current measuring instrument, the combination ofthe actuating coils, an adjustable reactance device included in thecircuit of one of said coils, and registering or indicating mechanismactuated by the currents in the said coils, and so adjusted as toregister or indicate a predetermined proportionate amount of wattlesscurrent.

3. In an alternating-current wattmeter, the

combination of the actuating-coils, a reactance device included incircuit with one of the said coils, and registering mechanism adj ustedso as to record the power delivered, and in addition thereto to record aportion ofthe wattless current.

These coils, closed on- IIO 4. In an alternating-current wattmeter, thecombination of the main-current coils, the potential-current coils, thearmature actuated by the current flowing in these respective coils, areactance device included in the potential-currentcircuit, andregistering mechanism adjusted to record accurately at noninductive loadthe power delivered, whereby a proportionate amount of the wattlesscurrent is registered in addition to the power delivered.

5. In an alternating-current system of electrical distribution, thecombination of the actuating-coils of a registering-wattmeter, anadjustable reactance device in circuit with one of the said coils, andregistering mechanism adjusted relatively to the reactance to recordwattless current in addition to energy current.

6. In an electric meter for alternatingcurrents, the combination of amotive device, the speed of which with loads of unity-power factor isproportional to the real energy, a recording mechanism controlledthereby, and means for increasing the speed of the motive device by apredetermined proportional amount when the load becomes lagging.

7. In an electric meter for alternating currents, the combination of amotive device, the speed of which with loads of unity-power factor isproportional to the real energy, a recording mechanism controlledthereby, and means for increasing the speed of the motive device by apredetermined proportional amount when the load becomes lagging and fordecreasing the speed of the motor when the load becomes leading.

8. In an alternatingcurrent meter, the combination of a motive deviceand registering mechanism for recording on loads of unitpower factor theenergy consumed in the circuit, with means for affecting the speed ofthe motor a desired part of the wattless current in adso as to recordupon inductive loadthe combination of a motor, recording mechanismdriven thereby, and speed-regulating means for said motor so adjusted asto cause the motor to run on lagging currents at a rate intermediatebetween such rates of speed as would correspond respectively tomeasurements of the apparent and actual energy of the load in theWork-circuit.

10. In an alternating-current-motor meter, the combination of a motor, arecording mechanism driven thereby, and speed-regulating means for saidmotor so adjusted as to cause the motor to run on lagging currents at arate intermediate between such rates of speed as would correspondrespectively to measurements of the apparent and actual energy of theload in the work-circuit, and on leading currents to run at a rate lessthan that corresponding to the actual energy.

11. A motor-meter having an armature provided with a commutator, and adevice possessing inductance in circuit with said armature.

12. An alternating-current electric motor constructed to measurewattless current in addition to energy current.

13. In an electric meter for alternating-current circuits, thecombination of a motive device, a recording device controlled thereby,and means for causing the speed of the motive device to be dependentupon the power factor of the circuit.

14. In an electric meter for alternating currents, the combination of amotive device the speed of which with loads of unity-power factorrepresents the real energ a recording mechanism controlled thereby, andmeans for causing the motive device to run faster when the load islagging than when the same amount of real energy is flowing atunity-power factor.

In witness whereof I have hereunto set my hand this 14th day of April,1902.

CHARLES P. STEINMETZ.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

